PERSONAL TRAINER INSTRUCTION :
Square off your shoulders to the cable in front. While keeping an upright position with a neutral spine, exhale and pull the cable handle back with one hand.
Focus on pulling through the elbow to activate the muscles of the back. Keep your shoulders depressed and the forearm parallel to the floor. Avoid twisting in the torso/spine through the exercise.
There are different variations that can be done with your hand positioning through the movement such as having your palm up (supinated) or palm down (pronated). Feel free to try and see what you like best. Any unilateral exercise activates the muscles of the core.